Re: rebase -i: Should --continue auto-amend after failed exec?

From: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Date: Aug 24, 2011, 13:36 UTC
Message-ID: <vpqk4a3rkwb.fsf@bauges.imag.fr>
In-Reply-To: <4E40511B.7090206@kdbg.org>

Johannes Sixt <j6t@kdbg.org> writes:

> If after a failed "exec" instruction there are staged changes, then currently rebase
> --continue fails with:
>
> .../git-rebase--interactive: line 774: .../.git/rebase-merge/author-script: No such file or directory

That's obviously bad, there should at least be an accurate error message.

Show 9 quoted lines

> But shouldn't this amend the HEAD commit? The documentation is not clear
> (from git-rebase.txt):
>
>   The interactive rebase will stop when a command fails (i.e. exits with
>   non-0 status) to give you an opportunity to fix the problem. You can
>   continue with `git rebase --continue`.
>
> This may be interpreted to work like "edit", and IMO would be a very useful
> modus operandi.

I'm not sure. What happens in "edit" is that when reaching the "edit" line, git-rebase--interactive.sh calls die_with_patch, which writes author information in .git/rebase-merge/author-script, which really means "I've stopped on this commit, this is the one that we should implicitely amend with --continue".

The case of "exec" is a bit different: you don't stop "on a commit", but after doing something else. You can hardly guess whether the staged changes are meant to amend the existing commit, or to make a new one.

Actually, that could even be

pick deadbeef Existing commit exec foo > bar.txt; git add bar.txt; git commit -m "added during rebase" exec false pick c00ffee Another commit

then auto-amending may be really confusing: should it amend the HEAD commit that you've just created (this would really go against the logic of .git/rebase-merge/author-script) or the last picked commit (which you can't really do since it's not HEAD)?

I think it's best to abort, with an accurate error message pointing the user to both solutions (commit --amend && rebase --continue or commit && rebase --continue). I'll try a patch.

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/